Capsulated bulb and method of making the same



Sept. 27, 1966 P. Q DEMAREST ET AL 3,275,879

- CAPSULATED BULB AND METHOD OF MAKING THE SAME Filed July 31, 1961 2 Sheets-Sheet l.

32 '36 INVENTORS,

PL'h/a flemar'esf, Harry R. Fosfer &, Elmo E. Crump ATTORNEY Sept.. 27, 1966 P. c. DEMAREST ET AL 3,275,879

CAPSULATED BULB AND METHOD OF MAKING THE SAME Filed July 31, 1961 2 Sheets-Sheet 2 NVENTORS.

PALZLp C..Demarest,

TTENEY United States Patent O 3,275,879 CAPSULATED BULB AND METHOD F MAKING THE SAME Philip C. Demarest, Pine Brook, Harry R. Foster, vMontville, and Elmo E. Crump, West Caldwell, NJ., assignors to Ohmega Laboratories, Pine Brook, NJ., a corporation of New Jersey Filed July 31, 1961, Ser. No. 128,245 1 Claim. (Cl. 313-317) This invention relates to capsulated bulbs or tubes which at some time during the production must be substantially gas-free. More particularly the invention relates to capsulated bulbs in which the presence of gas during the production thereof would be undesirable.

In order to exemplify the present invention it will hereinafter be described with relationship to a bulb of reduced size. It is, however, to be understood that this description is merely exemplary of the facets in which the present invention can be efficiently applied and that the description referring to miniaturiza-tion and microminiaturization is in no way to be construed as limiting the scope of the invention or the appended claims.

A serious problem .heretofore has existed in the production of bulbs which are extremely miniature in size. This has existed because of lthe presence of undesirable gas in the bulb at some time during its production. Such gas formations impair the eficiency and Vfunctioning of the bulb and prior to the present invention prevented the utilization of miniature and microminiature bulbs as a component in electronic devices for use in airplanes, rockets, missiles, the medical profession and various other areas of industry. The gas formation, as 'for example that caused by Water vapor and hydrogen emitted in the fusing of the gas bulb and effected in the seal of the bulb has heretofore seriously disturbed the functioning of bulbs of miniature size. The present invention, therefore, relates to and solves the problem of exhaustion of the undesirable gases Which vare formed during the production of the bulb itself. The invention contemplates the removal of all undesirable gases so that the bulb chamber may be gas-free if desired. However, by the use of the simple expeditious means utilized in the removal of lthe gases of undesirable nature it is also possible a-fter suc-h removal to insert into the bulb any gases Whose artificial introduction may add to the proper functioning of the bulb itself.

' In its broader aspects the present invention contemplates the provision of means in the Wall of the bulb itself through which the undesirable gas may be exhausted and While the gas is exhausted or after the introduction of desirable gas, the means themselves may be sealed ofi with the remainder of the bulb to provide a highly efficient gasfree or properly gas filled bulb.

More specifically, the present invention provides a miniature metallic tube of high resistance .to heat' and electricity :adapted to be passed through a Wall of the bulb and serve as a gas exhaust vent, and thereafter, if desired, as a gas intake tube. The tube is unaffected by the application Iof heat to fuse and seal the bulb and is itself thereafter closed and sealed as by the application of heat at a high temperature to fuse the walls of the tube.

' In carrying out the invention, the bulb is formed with an aperture for the assembly of the lament (and any other parts) in the bulb casing. A small-bore tube is formed of copper Wire clad or plated with platinum, which wire is then cut into short lengths and the cuttings subjected to a copper-etching acid bath until -the copper is completely etched from Within the platinum. The short platinum tube is then inserted in an aperture in the Wall of the bulb casing and secured therein. Heat is then applied to fuse the .area of the bulb around the filament assembly aperture to hermetically secure it inthe bulb. The

ice

position of the tube is such that one end opens into the bulb chamber and the other end opens exteriorly of the bulb, and under the influence of the vacuum the gas exhaustion continues to remove the gas generated by the fusing of the glass. `If desired proper gases may be introduced through the same tube. Thereafter the gas-free or appropriately gas filled bulb is finally prepared by hermetically sealing a portion of the tube by -heat fusing the walls of the tube. Thus the intake of air or undesirable gases or the escape of desirable gases through the tube is prevented. The bulb chamber is thus completely sealed.

In the accompanying drawings, the invention has been shown merely by way of example and in preferred form and obviously many variations and modifications may be made therein which will still be comprised within its spirit. It is to be understood, ltherefore, that the invention is not limited to any specific form or embodiment, except insofar as such limitations are set forth in the appended claims.

Referring to the drawings:

FIG. 1 shows a section of the wire employed for producing a metallic tube to be used in connection with the present invention;

FIG. 2 shows a tube formed from the wire shown in FIG. 1;

p FIG. 3 is a transverse section of a plastic mandrel wound with wire of the character shown in FIG. l;

FIG. 4 is a side elevation of the mandrel and wire Winding shown in FIG. 3 when encased in plastic material, and showing the slicing thereof into short sections of predetermined length;

FIG. 5 is a view showing a metal tube freely assembled with a short length of glass tubing;

FIG. 6 shows the metal tube surrounded by a ball into which the glass tube of FIG. 5 has been coalesced;

FIG. 7 shows the capsulated bulb with the glass balls assembled at both ends with one of said glass balls carrying the tubing provided by the present invention;

FIG. 8 shows the structure of FIG. 7 after the glass balls have been melted to form the final bulb With the tubing sealed off;

FIG. 9 shows the bulb in its preparatory state likev FIG. 7 with one of the leads passing through the glass balls at one side also constituting the tubing;

FIG. 10 shows a modified form of the present invention in which an electric resistance wire filament is attached to leads formed with a coalesced glass ball thereon assembled in the open end of the glass tubing;

FIG. 1l shows still another modified form ofthe present invention in which the leads are attached to cathodes with the leads formed with a coalesced glass ball thereon assembled in the open end of the glass tubing with a provision of, for example neon lights; and

FIG. 12 shows another modified form of the glass ball with the glass tubing coalesced into a ball around the leads into the filaments and assembled in the open end of the capsule.

In accordance with the preferred form of the present invention the bulbs or capsules of the microminiature electric device shown as exemplary herein is formed in a series of steps. Initially leads are secured passing through coalesced glass balls. A filament joins the interior portions of the leads and the balls are `inserted with one ball at each end of minute glass tubing. A source of electric current is passed through one of the leads producing enough heat to melt the glass ball and the contiguous part of the glass tube so that the glass ows together to make a hermetic junction and form a capsule. Thereafter the ends of the leads extend exteriorly of the capsule to serve as electrical terminals for the component within the capsule.

While the wire has been described as comprising two leads joined ltogether with an intermediate filament, the essential requirement is that bothends of the leads be available for connection to a source of electric current in order that the wire may be heated suiciently to melt the glass ball. The exact shape of the filament and leads is secondary to this basic requirement and it may adopt various forms as hereinafter described. The ball itself is formed in a series of steps according to the present invention, as for example by providing a short length of minute hollow glass tubing through which the lead is passed and thereafter applying a suitable voltage to the endsjof the leads to drive an electric current therethrough. This will heat the wire sutliciently to meltthe short pieces of glass tubing and cause it to coalesce into a ball which attaches itself to the leads and secures the lead within Vthe ball.

According to the present invention, successive manufacturing steps are involved, and after certain steps have been :performed the productV produced up to that point may` be -at a stage where it is suitablefor commercial marketing even -though additional steps haveto be yperformed in the production of the ultimate finished article. It is to lbe understood, therefore, that the inventionis not limited to the ultimate product or to the entire succession of steps involvedy in producing the capsulated electric lamp. Y

The present invention utilizes formed with a miniscule bore. According to a preferred procedure, and referring to FIGS. 1 to 4, a tube approximately 1/2 in length is produced with a miniscule bore approximately .0003" in diameter, although such dimensions may vary within a range of @/s" to 46 and of .005" to .0003, or less, respectively. The tube 10 is preferably made of platinum, and obviously itis too delicate to be made by machining, such as by dlilling or drawing. The preferred method of forming the tube 10 is -to clad a fine copper wire 11 with platinum 12 and drawing it down to the desired size. The plat-1 inum-clad wire 13 is then subjected to a bath in a copper-` etching acid-which will etch out or'erode away the copper` and thus produce the platinum tube.

Another problem is` presented in cutting the platinumclad Wire into predetermined short lengths, because it is essential that the cutting operation shall not compress the wire 13, whereby it might swage the platinum over the cut'end thereof and thereby prevent the etching out of the copper, to form the tube. Accordingly, it is proposed by the present invention to wind the platinum-clad lcopper wire 13 on a mandrel 14 formed of epoxy resin plastic or other suitable material which will be destroyed in the copper-etchingr acid bath.

Thus referring to FIGS. 1-4 a length of the platinumclad wire 13 is wound upon the mandrel 14 to build up a kWinding 15 of the .Wire thereon. When a sulicient winding I15 has been formed the mandrel 14 with its winding 15 is immersed in a bath of epoxy resin or other to encase the Winding and at the same time flow between and ensuitable material, heated to a uid condition,

case the `individual wires 13 of the winding. Upon removal from the plastic bath, the plastic chills to forma block-16 v'of plastic-encased wire (see FIGS. 3 and 4). The block 16,1may then be severed into slices a4' small metal *tube4 17 of pre- A n Y the platinum coating 12.1 The plastic is substantially destroyed by the acid `bathand the etched copper gives off determined thickness to form the desired lengths of platt intim-clad copper wire 13 without danger of collapsing the wire during the slicing operation. Thereafter `the. slices 17 may be sanded and polished to sulting platinum coating over the ends copper cores. The slices 17 are then placed in a heatedI bath of copper-etching acid. In an acid bath comprising approximately 50% nitric acid and 50% the plastic in the slices 17 will dissolve in approximately Water, which is heated to a temperature of approximately 100 to ll0C.,

remove any reof th dA e expose `glass bulb 30 and into the chamber 36 as shown. The lead,

therefore, also functions` as the tube itself through which4 the undesirable gases may be withdrawn prior topsealmgA hydrogen 'and salts, the hydrogen evolving as a gas and the salts going into solution in the bath. Thereafter the tubes 10 (FIG. 2) each formed by a platinum wall 20 surrounding a miniscule :bore 21, `are removed yfrom the acid bath and baked under vacuum in an oven heated to atem-perature in the range 15002000 F. for a period of approximately 4 to 5 hours to remove all gasin or on the surface of the metal.`

Preparation ofthe tube 10 for use in the formation of a bulb 25 for a capsulated electric lamp 35 (FIG.l 8) is shown in FIGS. 5 and 6. A preferred procedure isto cut from a length of .glass tubing a portion 27 fwhich is shorter than the length of the tube 10, insert the tube 10 into the portion 27 to bear against the inner surface and extend `beyond the `opposite ends thereof (FIG. 5), yand then by the application of heat to the portion 27. melt and cause the glass thereof to coalesce into a ball 28 ltightly lsealed around the tube 10 intermediate its opposite ends.

also provided.. A filament 32jextends between the` exposed portions of the leads or anchors 29 and 31 as shown. The unit is then placed within the glass tubing 33 so that the glass balls are disposed at each end thereof being preferably located `so that the `major portionl of each ball lies within the `tubing 33 at .its respective ends. The application of heat to the end of the tubing 33 `and the vballs 28 and 30 melts and causes them to fuse together at each end to form a permanent tight seal as, shown in FIG. 8 with the filament 32 permanently se,-`

cured therein. A capsulated bulb 35 -is'thereby provided.

In the fusing of the glass tubing 33 to secure the lila-` ment 32 therein, gas, which is primarily4 water and hydrogeu, is emitted into the chamber 36 of the bulb 35, and

according to the best practice known heretofore such gas would have become trapped in the chamber 36.` According to the present invention,'however, the gas is withdrawn through the tube 10 by the vacuum maintained around the` bulb V35, whereby the chamber 36 is. made substantially gasl free. While the bulb 35 .remains under the condition of vacuum, heat of suicient intensity is applied to a portion of the tube 10 exposed exteriorly of the 'bulb 35 (FIG. 8) to melt and fuse the walls thereof and hermetically seal the bulb 35. As already stated, the

withdrawal of substantially all gaspincluding that evolved in securing ythe filament 32 in place, enables the production of a capsulated electric lamp smaller than any whichy it has been possible to make heretofore.: Moreover, such lamps can be economically produced bythe use of multiple unit lamp jigs wherein a plurality of the bulbs 35 are assembled and closed, evacuated and sealed all `at the same,

time.

Another application of the present invention is shown in FIG. 9. In this instance` the bulb is formed substantially as'iheretofore described with the glass balls 28 and 30 being located within fthe glass tubing 33 and carrying leads 29, and 31 coalesced therein with the Vexposed inner portions being secured to a filament 32N, In this application of the present invention, however, the lead 31 `also comprises ya tubing whose bore 10a extends through the off the end of the tubing.

FIG. 10 discloses` another variant of the present in-V -vention. As shown, two leads 40 and 4L are `coalesced Within a glass ball 42 with the inner exposed ends thereof passing through the glass ball. A wire ilament 43 doubled back to form a open bight is secured to each of the ends of the filaments 40 and 41. By the application of heat, the glass ball and the glass tubing 44 are melted and fused at one end of the tubing 44. The platinum tube is utilized, at the end of the tubing 44 this section having been prepared as illustrated in FIG. 6 with the ball being fused and melted to the glass tubing 44. The application of heat to fuse the glass ball 42 and the tubing 44 will accomplish the final bulb.

FIG. 11 shows another modied lform of electric lamp wherein the leads 50 and S11 coalesced Within the glass ball 52 carry cathodes 53 and 54. In this construction, after the yundesirable gases are withdrawn from the chamber 55 through the tubing 10, a desirable gas, such as neon, may be introduced into the chamber through the tubing 10 before the tubing is sealed off to form a completely'sealed capsulated neon lamp. It may be seen :that the present invention contemplates the withdrawal of undesirable gases at any time during the production of the lamp and that if desirable gases are necessary they may be introduced through the same means used to withdraw the undesirable gases. Thus, many types and kinds of bulbs may be formed under this present invention.

Another application of the present invention is shown in FIG. 12 wherein a lamp element 60 is rformed closed at one end and open at the other end. lIn this instance the t-ube '10 and lament 61 are both assembled in the open end of the glass tubing encased in a glass ball 62 With leads 63 and 64 passing through the ball attached to the efilament. When heat is applied to the ball and the surrounding portion of the yglass tubing, a tight seal is formed which also insulates the leads and the tubing one from the other. After the gas is withdrawn, the exposed end of the tube 10 is lfused to seal the bulb 60.

-In the foregoing specification and in the appended claims, the word bulb as used includes any incandescent lamp, electronic tube, or other such article which requires that the interior thereof at some time during its construction be in a condition of substantial vacuum, i.e., exhausted or substantially exhausted of air or gas. It is also intended that the word gas shall include various different types of gases.

As already stated, prerferred embodiments of the invention have been shown and described herein and many modications and variations thereof may be made. Furthermore, different modes of application of the invention may occur to those skilled in the art without departing from its spirit. rTherefore, it is to be Iunderstood that the appended claim is not to be construed as being limited beyond the scope of the language expressly set forth therein.

We claim:

A capsulated bulb comprising: a substantially cyli-ndrical glass Wall pervious to light; a :line metal filament Within Isaid bulb; two separately-formed glass end members `fused to said substantially cylindrical glass Wall, one at each end, and each of said members having an axial thickness substantially greater than the thickness of said Wall; vtwo relatively heavy metal wires substantially parallel to the axis of said cylindrical Wall, one of said wires extending through each of said end members and having an end of each of said relatively heavy Wires electrically and mechanically attached to one end, respectively, orf said ilament to support said ilament Within the space of said bulb; a tube of fusible metal `formed with a miniscule I bore and hermetically sealed into one of said end members and extend-ing substantially parallel to the axis of said bulb and spaced from said relatively 'heavy Wire, with one end of said tube opening interiorly of said bulb to evacuate gas trom said bulb, said bulb having a substantially gas-free interior.

References Cited by the Examiner UNITED STATES PATENTS 586,055 7/ 1897 Olam 313--222 2,087,754 7/ 1937 Davies 3113-220 2,097,679 11/ 1937 Swanson 313-222 X 2,154,542 4/ 1939 Swanson 313--222 X 2,185,025 1-2/ 1939 Elenbaas et al 313-222 X 2,438,721 3/ 1948 Spencer 316-19 2,449,676 9/ 1948 Seitz -3 16-19 2,5 68,459 9/ 1951 Noel 3 13-220 2,664,517 12/ 195 3 Wiener 313--220 X `2,845,568 7/ 1958 West et al 313-220 X HERMAN KARL SAALBACH, Primary Examiner. GEORGE WESTBY, ARTHUR GAUSS, Examiners. SAXFLELD CHATMON, IR., Assistant Examiner. 

